Nitrogen Blanketing System

ABSTRACT

A nitrogen blanket system for small fuel tanks is disclosed that includes tank empty-space pressure control for sealed tanks that can hold pressure. The system includes a fuel tank storing some volume of fuel, such as diesel fuel. The remaining empty volume is filled with nitrogen by the disclosed system. The nitrogen blankets the liquid fuel and fills the remaining space in the fuel tank to prevent the accumulation of moisture and thereby prevent corrosion within the fuel tank.

BACKGROUND Technical Field

The present disclosure relates generally to systems and methodsassociated with fuel tanks configured for storing fuel, and moreparticularly to systems and methods associated with preventing corrosionwithin fuel tanks.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the system of the presentapplication are set forth in the appended claims. However, the systemitself, as well as a preferred mode of use, and further objectives andadvantages thereof, will best be understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings, in which the leftmost significant digit(s) in thereference numerals denote(s) the first figure in which the respectivereference numerals appear, wherein:

FIG. 1 shows a block diagram of a nitrogen blanket system according tothe present application;

FIG. 2 shows a schematic block diagram of a nitrogen vending stationaccording to the present application; and

FIG. 3 shows a schematic view of an alternative embodiment of a fueltank for the system shown in FIG. 1.

While the system of the present application is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the method to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the application as defined by the appendedclaims.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the system of the present application aredescribed below. In the interest of clarity, not all features of anactual implementation are described in this specification. It will ofcourse be appreciated that in the development of any such actualembodiment, numerous implementation-specific decisions must be made toachieve the developer's specific goals, such as compliance withsystem-related and business-related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, apparatuses, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms such as “above,” “below,”“upper,” “lower,” or other like terms to describe a spatial relationshipbetween various components or to describe the spatial orientation ofaspects of such components should be understood to describe a relativerelationship between the components or a spatial orientation of aspectsof such components, respectively, as the device described herein may beoriented in any desired direction.

Referring to FIG. 1, a schematic block diagram of a nitrogen blanketingand fuel treatment system 100 is shown. A number of above and belowground Ultra-low-sulfur diesel (ULSD) fuel storage tanks regionally areexhibiting expected signs of a “Debris Cauldron Effect” that potentiallypresents a condition that (to date) is regionally degrading internalstorage tank primary containment boundaries, internal tank componentsand fittings, product delivery piping, dispenser emergency shear valveinternal sealing and seating platforms, dispenser control flow valves,nozzles, hanging hardware components, dispenser filters, and meteringdevices. This often occurs because, as fuel is pumped out of the fueltank, it is displaced by air, which introduces moisture into the tank.

Disclosed herein is a nitrogen blanketing system 100 for small fueltanks that includes tank empty space pressure control for sealed tanksthat by design will hold pressure. Small fuel tanks as described hereinrefer generally to low-pressure fuel tanks no larger than 50,000 gallonsand rated for storing fluid at 5 pounds per square inch (psi) or less,including small retail fuel tanks such as those commonly used asunderground storage tanks at retail gas stations, which typically have acapacity of no more than about 30,000 gallons. The system 100 includes afuel tank 101 storing some volume of fuel 102, such as diesel fuel. Theremaining empty volume 103 is filled with nitrogen by the disclosedsystem 100. The nitrogen is provided by a nitrogen generation system110. The nitrogen generation system 110 includes a nitrogen generator104 that is driven by a regulated air compressor 105. The regulated aircompressor 105 supplies compressed air through a regulatedcompressed-air reserve tank 106 and via a conduit to an air dryer 107.The air dryer 107 reduces the amount of moisture in the receivedcompressed air, and then supplies the thus-dried air to an air regulator108 via a conduit, where pressure of the dried air is further regulated.The air from the regulator 108 is then supplied via another conduit tothe nitrogen generator 104 where, through a pressure swing absorptionmethod known in the art, the nitrogen generator 104 produces pressurizednitrogen.

The nitrogen from generator 104 flows under pressure via a conduit to anitrogen reserve buffer tank 109. Nitrogen from the tank 109 and fromthe generator 104 also flows via conduit 114 to the fuel tank 101. Thepressure of the nitrogen from the generator 104 and tank 109 iscontrolled by a nitrogen pressure regulator 111 and a pressure-sensingswitch 112. Nitrogen at the controlled sensed pressure flows from thepressure-sensing switch 112 via a conduit and a coupling 113 into theconduit 114. The nitrogen then flows via the conduit 114 to a nozzle115, and then into the empty space 103 (also referred to as headspace)of the fuel tank 101, blanketing the fuel 102 that is stored therein.While a single nozzle 115 is shown in FIG. 1, alternative embodimentscan include a plurality of nozzles 115. The number of nozzles can bedependent on the size of the tank; for example a tank can have betweenone and twelve nozzles depending on the size of the tank. Apressure-sensing tank differential switch 116 is in constantcommunication with the conduit for monitoring pressure in the conduit114 and the empty space 103 of the tank. The switch 116 is ordinarilyclosed, thereby blocking the flow of nitrogen. However, if the switch116 detects excess pressure in the conduit 114, for example if thepressure in the fuel tank exceeds a prescribed amount, then the switch116 opens to allow nitrogen to vent through a pressure vacuum valve 117.The nitrogen in the empty space 103 is referred to as blanketingnitrogen that blankets the fuel 102 and advantageously reduces orprevents moisture from accumulating in the fuel tank 101.

The pressure-sensing switch 112 and differential switch 116 are bothfluidly connected to the headspace 103 of the tank 101 and areconfigured for maintaining an adequate amount of atmospheric pressure inthe headspace 103. Headspace pressure set as low as 1 inch of watercolumn can be sufficient. As the tank 101 discharges fuel 102 and liquidfuel level in the tank 101 drops, the atmospheric pressure in theheadspace 103 can sometimes drop below a first threshold amount, causingthe switch 112 to open to allow nitrogen from the generator 104 and/ortank 109 to be added to the headspace 103 until the atmospheric pressurein the tank 101 exceeds the first threshold amount, at which point theswitch 112 closes to stop the flow of nitrogen from the generator 104and/or tank 109 to the tank 101. As the tank 101 is filled with the fuel102, the pressure in the headspace 103 can sometimes increase beyond asecond threshold amount, causing the switch 116 to open so that excessnitrogen can exit through the venting valve 117 via the conduit 114until the atmospheric pressure in the tank 101 drops below the secondthreshold amount, at which point the switch 116 closes to preventnitrogen from exiting the tank 101 via the conduit 114 and the ventingvalve 117.

In some embodiments, the tank 101 can be a small retail fuel tank, e.g.,an underground fuel tank at a retail gas station. In such embodiments,the tank 101 can further be in fluid communication with other componentscommonly associated with such small retail fuel tanks, such as a tankfill riser 118 and a fuel dispenser 119. The fuel riser 118 can be usedfor venting the fuel tank 101 and/or for adding fuel 102 to the fueltank 101. The fuel dispenser 119 is used for removing fuel 102 from thetank 101, for example for allowing a consumer to add fuel 102 to avehicle.

The readily-available supplies of nitrogen, combined with the relativelylow cost of inert nitrogen, makes the process of environmental controltank blanketing with inert gas financially advantageous. The desiredamount of inert gas volumes can be calculated by the system 100 usingknown standard formulas.

According to the present disclosure, it is preferable to safely storeand connect to a tank of compressed inert gas where it may be in closeproximity to fueling customers.

Serviceable storage, dispensing and system component integrity is beingeffected by a complicated set of constituents and conditions introducedand or existing in ULSD storage tanks. Combinations in some cases areunique and in others a cauldron mix of complicated solution(s) andgeometric variables not well understood. While cross contaminatedethanol could be blamed for the bulk of the surfacing concerns, mosthave concluded that it is somewhat more complicated. Recent industryreports and surveys have described the storage tanks problemenvironments with (to date) not pointing a resolution(s) path. Also,since the use of alcohols being added to gasoline products became morewidespread, there has been a sensitivity to reducing the potential forwater to mix with the gasohol as the alcohol will absorb the water as itenters the fuel distribution system. Problems occur when the alcoholcontent reaches a saturation level at a specific temperature. If thetemperature of the fuel drops (typically due to environmental reasons),the alcohol/water mix will separate and drop to the bottom of the tank.This process is referred to as phase separation. This new liquid is morecorrosive as the alcohol content is significantly higher. This newliquid also has the alcohol and water to supply the needed nutrients tosupport microbial growth.

Environmental control blanket nitrogen inerting of ULSD fuel storagetank empty space provides an advantageous way to protect components andprevent, control, or inhibit tank ullage space acetic acid corrosion.Blanket nitrogen inerting prevents ingestion of atmospheric air andmoisture in hydrocarbon fuel storage tanks and avoids empty spaceformation of hydrocarbon vapor and corrosion. As a result, nitrogenblanketing can reduce the amount of hydrocarbons being released into theatmosphere through venting systems of such tanks. Another benefit toinerting the headspace of a fuel storage tank with nitrogen is that itreduces the chance of a flash fire, such as those that regularly occurin fuel tanks due to lightning strikes to the vents or other metallicconnections to the headspace of the tank or from static discharge fromfueling or filling that be in communication with the head space of atank, both of these are known and identified problems in the industry.

The disclosed system can be used with various different types of fueltanks, including diesel fuel tanks at retail gas stations. Other fueltanks can include tanker trucks, railcars, ocean-going vessels, andocean platforms. The disclosed system can be used with above-ground fueltanks and below-ground fuel tanks.

The disclosed system can also be used for pressure-testing a fuel tank.Sensors in the system can be used for monitoring various characteristicsof the system and the fuel, such as the blend of the fuel and the amountof moisture in the tank. Sensors can also be associated with thepressure gauge for remote monitoring of the amount of pressure in thefuel tank. The data from the sensors can be transmitted for remotemonitoring and can be stored in a database.

The system shown in FIG. 1 is not limited to fixed tanks, but can alsobe applied to mobile tanks, such as tanks on rail cars, trucks, andships. Such mobile systems can be configured substantially the same asshown in FIG. 1. Power for mobile systems can include solar powersystems and/or vehicular power systems.

In addition, the presence of nitrogen in the conduit 114 also reduces oreliminates the build-up of moisture in the conduit itself, therebyreducing or eliminating corrosion of the conduit 114. It shouldtherefore be appreciated that in some embodiments, the conduit 114 canbe a conduit that extends several meters or several kilometers or evenlonger, and that the system 100 can be modified to prevent corrosion inconduits that provide for the transport of fluids, including liquidpetroleum-based products such as fuel or oil, across any distance. Forexample, the system 100 can be used to provide blanketing nitrogen in astorage tank 101 as well as a conduit that extends between the tank 101and a distant pumping or drilling station, and that the nitrogen in theconduit will fill the empty space therein to prevent the buildup ofmoisture therein.

In some embodiments, the system 100 can further include a coatingdispenser 130 for injecting a substance for coating the inside of thetank 101, such as a volatile corrosion inhibitor (VCI). For example, onecommon set of materials used to coat fuel (particularly hydrocarbonbased) tanks includes ZERUST product provided by Northern TechnologiesInternational Corporation of Circle Pines, Minn. Zerust VCIs are infusedinto a stable base material—like polyethylene (plastic) sheets. Whendeployed, VCIs are released from the base/delivery material and amolecular layer of VCI is deposited on the surface of the metal to beprotected. Zerust VCIs act in one of the following ways—or a combinationof these mechanisms depending on the application: 1. Barrier Film: Wherethe molecular layer prevents corrosive elements from reaching the metal.In some cases, this may also be in the form of a passivation film. 2. pHAltering: Where the VCI molecules alter the pH of the layer in contactwith the metal and prevent corrosion 3. Scavenging: Where the VCImolecules react with the corrosive elements in the environment andconvert them into neutral compounds.

VCI products can prevent corrosion in several ways: by acting as aprotective barrier from external dirt and abrasion, and also by actingas a barrier to help block the diffusion of corrosive acid gaspollutants from outside the VCI packaging material (such as sulfurdioxide or hydrogen sulfide)—thereby preventing contact of thesecorrosive gases with enclosed metal surfaces. Vas can also act as avapor corrosion inhibitor that passivates the electron flow between theanodic and cathodic areas on metal surfaces and interrupts theelectro-chemical corrosion process. VCIs can also add water-repulsionproperties to the metal surface, which inhibits water from permeatingthe metal surface and providing the electrolyte for corrosion reactions.

The vapor corrosion inhibitor portion of VCI products are known that aremade of chemical formulations that are invisible, odorless, non-toxic,non-reactive, non-flammable and/or non-allergenic. These chemicalformulations can release a corrosion-inhibiting vapor that diffusesthroughout an enclosure and settles on exposed metal surfaces to form amicroscopic corrosion inhibiting layer. This protective layer willremain on the surface of the metal as long as there is no significant,continuous exchange of air within the enclosure. Ideally, there shouldbe less than one air exchange per day (for example, when an electricalcabinet or package is opened briefly and occasionally). Once the metalpart is removed from the enclosure, the corrosion inhibiting layer is nolonger kept in place by equilibrium with the VCI source, and itdissipates from metal surfaces (typically within about an hour) leavingthe metal part clean, dry and corrosion-free.

Some known VCIs are water-based rust preventative compounds. They can bedesigned for use as foggable protection for the inside void spaces oftanks, packages and enclosures. They can be suitable for protectingferrous metals and/or multimetal materials. VCI foggable aqueous-basedrust preventative liquids are known that can protect ferrous metals viacontact inhibitors. They can also be used as a pressurized spray. VCImolecules migrate to provide protection on even hard to reach areaswithin an enclosed space. The rust preventative forms a clear, thin,dry-to-touch coating and some known VCIs are safe for use on mostpainted surfaces, rubber seals, and plastics, and/or can be compatiblewith other metals such as aluminum, copper, brass, and nickel alloys.

The system 100 advantageously can be used to incorporate VCIs in fuelsystems. The system 100 can use the disclosed gas blanketing system todisperse a VCI from dispenser 130 onto surfaces in the fuel tank 101 andother fluidly-connected components, such as conduit 114, vent conduit118, and fuel dispenser 119. VCI from dispenser 130 can be dispersedalong with the inert or blanketing gas into the tank 101 to provide forcoating of system surfaces. By integrating with the blanketing system100, the tank 101 and supply conduits can be provided with a consistentamount of VCI. Alternatively, the Vas may be introduced as needed at oneor more particular time or interval.

The dispenser 130 can include a VCI storage/source tied into amicroprocessor-based controller that is configured to dispense VCImaterial in conjunction with the dispersal of nitrogen into the tank 101such that the nitrogen can provide for a carrier of VCI (e.g. in fogform) into the tank 101. By utilizing the Vinturi effect, anon-pressurized VCI source can be drawn into the conduit 114 and intothe tank 101 and mix properly with the blanketing gas to evenly coat thetank ullage and supply lines.

In the alternative, the VCI can be pressurize and introduced with theblanketing gas, or otherwise introduced alone or sprayed onto tank wall.The introduction and application of VCIs may comprise a separate eventto deliver a predetermined level of VCI into the system. VCIs may alsobe sent as a pressurized spray to coat tank and cause the pressurerelief system to open in the tank, and thereby force gases out of theullage and the relief line. By coating the pressure relief line, itprevents rust on the upper portions of the fuel storage system andprevents rust from breaking off and falling back into the fuel.

Vas also serve to coat and protect sulfur dioxide from diesel exhaust ina vehicle motor to prevent acid (i.e. sulfuric acid) from eating upvehicle tanks and motor system tubing. VCIs can be used on dieselexhaust fluid and used to line tanks on trucks.

Referring now also to FIG. 2, in embodiments where the system 100 isused in a retail environment, the nitrogen generation system 110 can beused to provide nitrogen for a nitrogen vending station 120. Thenitrogen vending station 120 can be a point-of-sale unit that allowsconsumers to fill nitrogen-filled automobile tires. The nitrogen vendingstation 120 can include an air hose 124 configured with a valve andnozzle for allowing a user to inflate standard automobile tires withnitrogen. The nitrogen vending station 120 can also include a paymentsystem for allowing a consumer to make a payment, for example via cash,coins, and/or credit card. In such embodiments, the payment system canbe configured to only allow nitrogen to be dispensed via the air hose124 once payment has been made. Also, the vending station 120 can limitthe amount of nitrogen that is dispensed once payment is made, forexample based on a predetermined amount of time or based on apredetermined amount of nitrogen. The nitrogen vending station 120 canalso include an override control 128 for allowing service stationpersonnel to override the need for a consumer to make a payment andallow the vending station 120 to dispense nitrogen without payment orotherwise allow for free nitrogen from the vending station 120.Alternatively, the nitrogen vending station 120 can be a self-containedor stand-alone system that includes a dedicated nitrogen generationsystem 110 that only provides nitrogen for the nitrogen vending station120.

The nitrogen generation system 110 can be used in additionalapplications where the moisture-reducing benefits of displacing air withnitrogen is beneficial. For example, the nitrogen generation system 110can be used in connection with networks of electrical conduit to forceair out of the conduit and replace the air with nitrogen in order toreduce the amount of moisture in the conduit lines. Alternative examplesinclude the use of the nitrogen generation system 110 for forcingnitrogen into the headspace of plumbing tanks and traps, HVAC systems,septic systems, and grease traps. The use of nitrogen to replace air insuch systems can advantageously reduce moisture buildup and microbialgrowth in such systems.

Also, the nitrogen generation system 110 can be used in connection withemergency systems where it may be advantageous to reduce the oxygenlevel in the event of a fire emergency. For example, the nitrogengeneration system 110 can be configured in communication with anemergency detection system, such as an alarm system or the like, and canbe configured to force nitrogen into a room, container, airbag, or anydesired space in response to a trigger signal from the emergencydetection system.

Over time, some fuels that contain ethanol tend to absorb water. Sourcesof the absorbed water can include the introduction of liquid water orhumidity in the headspace of a vessel, such as an above- or below-groundfuel storage tank, shipping vessel, or vehicle fuel tank. Thisabsorption can occur during manufacturing, shipping, and storage of thefuel. This combination of water with the fuel can lead to a phenomenonknown as phase separation, where the water and fuel will form separatelayers within a tank. Once phase separation occurs, it can lead toseveral problems. In a vehicle, for example, the engine could fail tostart or could operate poorly or inefficiently due to the intake ofwater or intake of fuel containing water. In storage tanks, thedispensed fuel containing water will combust inefficiently andcomponents of the fuel containment systems can suffer from acceleratedcorrosion due to the unanticipated water levels in the fuel.

The treatment system disclosed herein provides a system and method fortreating fuel by introducing nitrogen into the fuel for the purpose ofremoving water from the fuel. Referring specifically to FIG. 3, analternative fuel tank 200 is shown that can be used with the system 100in place of, or in addition to, the fuel tank shown in FIG. 1. The fueltank 200 is particularly useful for implementation of such a fueltreatment system. The fuel tank 200 includes a conduit 210 that extendsalong the bottom of the tank 200. The conduit 210 includes one or moreapertures 220. The conduit 210 is in fluid communication with thenitrogen generation system 110. More specifically, the conduit 210 canbe in fluid communication with the conduit 114 shown in FIG. 1,downstream of the coupling 113 shown in FIG. 1. The conduit 210 receivesnitrogen from the nitrogen generation system 110 and dispenses thereceived nitrogen into the tank 200 from the bottom of the tank 200,through any fuel 230 in the tank 200, to the headspace 240 of the tank200. The tank 200 can otherwise be the same as the tank shown in FIG. 1,for example including a fuel dispenser conduit 250 to fuel dispenser 119and tank vent conduit 118.

In some embodiments, the treatment system can include one or moresensors 270 for measuring the amount of water in the fuel. The one ormore sensors 270 can provide data to a controller 280, which in turn cancontrol the amount of nitrogen being pumped into the fuel via thenitrogen generation system 110. For example, the controller 280 can be amicroprocessor-based device that is configured to control the operationof the nitrogen generation system 110 by activating the nitrogengeneration system 110 when data from sensor 270 indicates that waterseparation operations are needed, and also by controlling the volume andrate at which nitrogen is introduced into the fuel tank 200 depending onwhether data from sensor 270 indicates that water separation operationsare needed.

The treatment system can also include one or more agitators 290 foragitating the fuel 230 in order to improve the mixing of nitrogen withthe fuel 230, and thereby improve the removal of water from the fuel bythe nitrogen. The controller 280 can be configured to control theoperation of the one or more agitators 290 by activating them when datafrom sensor 270 indicates that water separation operations are needed,and also by controlling the speed of the agitator(s) 290 in order toadjust the rate at which nitrogen is mixed with the fuel 230 dependingon whether data from sensor 270 indicates that water separationoperations are needed.

The particular embodiments disclosed above are illustrative only, as theapplication may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of theapplication. Accordingly, the protection sought herein is as set forthin the claims below. It is apparent that a system with significantadvantages has been described and illustrated. Although the system ofthe present application is shown in a limited number of forms, it is notlimited to just these forms, but is amenable to various changes andmodifications without departing from the spirit thereof.

What is claimed is:
 1. A nitrogen blanketing system for a fuel tank, thesystem comprising: a nitrogen generator; a pressure-sensing switch influid communication with the nitrogen generator; a conduit for providinga fluid path between the pressure-sensing switch and the fuel tank; anda differential switch in fluid communication with the fuel tank via theconduit; wherein the pressure-sensing switch is configured to close toprevent nitrogen from flowing from the nitrogen generator to the fueltank if atmospheric pressure in the fuel tank is above a firstpredetermined level, and configured to open to allow nitrogen to flowfrom the nitrogen generator to the fuel tank if atmospheric pressure inthe fuel tank is below the first predetermined level; and wherein thedifferential switch is configured to open to allow nitrogen to escapefrom the fuel tank via the conduit if atmospheric pressure in the fueltank is above a second predetermined level, and configured to close toprevent nitrogen from escaping from the fuel tank via the conduit ifatmospheric pressure in the fuel tank is below the second predeterminedlevel.
 2. The system of claim 1, further comprising: a dispenser influid communication with the tank via the conduit.
 3. The system ofclaim 2, wherein the dispenser is configured to dispense a volatilecorrosion inhibitor into the tank while nitrogen is flowing in theconduit towards the tank.
 4. The system of claim 1, further comprising:a pressure vacuum valve in fluid communication with the tank via theconduit while the differential switch is open.
 5. The system of claim 1,further comprising: a buffer tank in fluid communication with thenitrogen generator and the pressure-sensing switch.
 6. A system,comprising: a nitrogen blanketing system for a fuel tank, the systemcomprising: a nitrogen generator; a pressure-sensing switch in fluidcommunication with the nitrogen generator; a conduit for providing afluid path between the pressure-sensing switch and the fuel tank; and adifferential switch in fluid communication with the fuel tank via theconduit; wherein the pressure-sensing switch is configured to close toprevent nitrogen from flowing from the nitrogen generator to the fueltank if atmospheric pressure in the fuel tank is above a firstpredetermined level, and configured to open to allow nitrogen to flowfrom the nitrogen generator to the fuel tank if atmospheric pressure inthe fuel tank is below the first predetermined level; and wherein thedifferential switch is configured to open to allow nitrogen to escapefrom the fuel tank via the conduit if atmospheric pressure in the fueltank is above a second predetermined level, and configured to close toprevent nitrogen from escaping from the fuel tank via the conduit ifatmospheric pressure in the fuel tank is below the second predeterminedlevel; and a nitrogen vending station comprising: an air hose in fluidcommunication with the nitrogen generator; and a user-operable valve forcontrolling the flow of nitrogen from the air hose.
 7. The system ofclaim 6, wherein the nitrogen vending station further comprises: apayment system configured to prohibit nitrogen from flowing from thenitrogen generator through the air hose unless a payment has been madevia the payment system.
 8. The system of claim 7, further comprising: anoverride switch to override the payment system and allow nitrogen toflow from the nitrogen generator through the air hose without a paymenthaving first been made via the payment system.
 9. A system, comprising:a fuel tank configured to store liquid fuel; a nitrogen generator; apressure-sensing switch in fluid communication with the nitrogengenerator; a conduit for providing a fluid path between thepressure-sensing switch and the fuel tank; and a differential switch influid communication with the fuel tank via the conduit; wherein theconduit extends along the bottom of the fuel tank and includes aplurality of apertures for dispensing nitrogen from the nitrogengenerator such that the nitrogen is dispensed into liquid fuel if liquidfuel is present in the fuel tank.
 10. The system of claim 9, wherein thepressure-sensing switch is configured to close to prevent nitrogen fromflowing from the nitrogen generator to the fuel tank if atmosphericpressure in the fuel tank is above a first predetermined level, andconfigured to open to allow nitrogen to flow from the nitrogen generatorto the fuel tank if atmospheric pressure in the fuel tank is below thefirst predetermined level.
 11. The system of claim 9, wherein thedifferential switch is configured to open to allow nitrogen to escapefrom the fuel tank via the conduit if atmospheric pressure in the fueltank is above a second predetermined level, and configured to close toprevent nitrogen from escaping from the fuel tank via the conduit ifatmospheric pressure in the fuel tank is below the second predeterminedlevel.
 12. The system of claim 11, further comprising: a pressure vacuumvalve in fluid communication with the tank via the conduit while thedifferential switch is open.
 13. The system of claim 9, furthercomprising: a buffer tank in fluid communication with the nitrogengenerator and the pressure-sensing switch.
 14. The system of claim 9,further comprising: a dispenser in fluid communication with the tank viathe conduit.
 15. The system of claim 14, wherein the dispenser isconfigured to dispense a volatile corrosion inhibitor into the tankwhile nitrogen is flowing in the conduit towards the tank.
 16. Thesystem of claim 9, further comprising: an agitator for agitating liquidfuel stored in the fuel tank while nitrogen is flowing from the conduitinto the fuel tank.